1. Field of The Invention
The invention relates to stacked type connector assembly, and particularly to the connector having the densely arranged solder tails thereof.
2. The Related Art
U.S. Pat. No. 6,126,472 having the same applicant and the same assignee with the invention, discloses two SO DIMM (Small Outline Dual In-line Memory Module) connectors stacked with each other for receiving the two modules, respectively, wherein each of connectors includes upper row and lower row contacts respectively forwardly and rearwardly inserted into and then received in the upper and lower passageways of the corresponding housing. Anyhow, it is noted that in the SO DIMM connector, the upper row contacts and the lower row contacts are staggered with each other, i.e., of a zigzag manner along a longitudinal direction of the connector, as shown in FIG. 6 of U.S. Pat. No. 6,419,513 having the same applicant and the same assignee with the invention, for compliance with the corresponding circuit pads on the lower edge section of the daughter printed circuit board which is received in the central slot of the connector. Additionally, because the adjacent two contacts are spaced from each other with about 0.6 mm, it is required to have tail sections of the adjacent two contacts further staggered with each other along the longitudinal direction of the connector for keeping enough space between every adjacent two solder sections, for avoiding interference between such solder sections while still keeping the whole with the compact region thereof, on the mother printed circuit board on which the connector is mounted. Therefore, there should be four lines of the solder sections applied on the mother board and no any two of such four lines of the solder sections are not aligned with each other in a front-to-back direction.
FIG. 1 shows an approach following this principle, which is disclosed in FIG. 4 of the copending application Ser. No. 10/215,313 filed Aug. 7, 2002, and discloses a design of denser arrangement of the solder tails of the contacts in comparison with the aforementioned U.S. Pat. No. 6,126,472, with the same applicant and the same assignee as the invention, where corresponding to the solder sections/pads on the corresponding mother board, every solder ball 100 on the solder tail of the contact in the connector has its own longitudinal position along the longitudinal direction of the connector and no any (adjacent) two solder balls are aligned with each other in the front-to-back direction. Understandably, there is no problem for its electrical function. Anyhow, sometimes this somewhat odd arrangement may make it little difficult for the designer of the mother board circuit trace layout because he might need to use the irregular routing for each solder sections/pads to escape from the adjacent solder section/pads for no interference therebetween. This makes it difficult and complex in the circuit trace layout design. Accordingly, it is desired to provide a new tail arrangement of the contacts of the SO DIMM connector, which allows an easy and systematic/scientific arrangement of the corresponding solder sections/pads on the mother board.
According to an aspect of the invention, a SO DIMM connector includes an insulative housing defining a central slot with upper and lower rows of passageways by two sides thereof. The upper passageways and the lower passageways are staggered with each other along a longitudinal direction of the housing. Upper and lower rows of contacts are respectively received in the corresponding upper and lower passageways, respectively. Each contact has a contact portion extending into the central slot for engagement with the corresponding circuit pad on a lower edge portion of the daughter board received within the central slot, a retention portion for retaining the contact in the housing, and a mounting pad, i.e., the tail portion, bent at a right angle relative to the main body of the contact. The mounting pads of the two adjacent two contacts in the same upper or lower row are staggered with each other along the longitudinal direction of the housing while the mounting pads of the upper row contacts are bent at a right angle in a first direction which is opposite to a second direction along which the mounting pads of the lower row contacts are bent at a right angle. Therefore, there are four lines of the mounting pads of the upper and lower contacts along the longitudinal direction wherein the mounting pad of one contact in one row is substantially aligned with the corresponding mounting pad of one contact in another row in a front-to-back direction so that the corresponding solder pads, i.e., solder section, on the mother board can be arranged in a relatively neat manner for allowing easy routing of the circuit traces thereof.
Another aspect of the invention includes the installation sequence of the contacts, wherein the upper row contacts are forwardly inserted into the housing from the rear face of the housing and the lower contacts are rearwardly inserted into the housing from the front face of the housing under a condition that the contacts with the inner mounting pads of each row contacts are inserted into the housing prior to those with the outer mounting pads so as to avoid obstruction of installation of the contacts if in a reverse order. This requirement results from the mounting pad of each contact being overlapped with those of two opposite neighboring contacts in the front-to-back direction.
Another feature of the invention provides the mounting pads with the solder balls thereon as disclosed in the aforementioned copending application Ser. No. 10/215,313, wherein the application of the solder ball can be referred to U.S. Pat. No. 6,220,884 having the same assignee with in this invention.